The present invention generally relates to an air bag and more specifically to a means for controlling the inflation rate of the air bag.
As it is known in the art, the air bag must be able to be filled rapidly to protect the occupant but slow enough to limit the forces imparted to the occupant, especially the out-of-position occupant. Various techniques have been suggested, in the prior art, to control the rate of inflation of an air bag as well as the trajectory it will take upon inflation. Such techniques include controlling the rate at which an inflator provides inflation gas, using tethers which effectively slows inflation, the use of coated, partially coated and or uncoated fabric with various levels of porosity which permit some of the inflation gas to be exhausted. As can be appreciated, it is desirable to be able to control the rate of the air bag inflation, such that its impact especially with an out-of-position occupant is within certain design limits. The present invention is directed to one such means of controlling the rate of inflation.
Accordingly, the invention comprises: an air bag adapted to be inflated comprising: an inlet portion to receive inflation gas and a flexible walled portion including at least one first vent hole therein. A flexible member is joined at one end thereof to the walled portion on one side of the first vent hole and at another end thereof to the walled portion on an opposite side of the first vent hole. The flexible member includes at least a second vent hole. The air bag includes first means, formed in the flexible member and the walled portion for maintaining the first and second vent holes aligned during an initial phase of inflation so as to provide exhaust port through which inflation gas may exit and for permitting the first and second vent holes to move relatively to one another during continued inflation so as to close the exhaust port. In the preferred embodiment of the invention, the first means includes a plurality of expansion joints formed in both the walled portion of the air bag and in the flexible member. As the air bag continues to inflate, the aligned vent holes are permitted to move relative to one another as the expansion joints expand so as to effectively close gas flow therethrough.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.